Answer: The tone is thrilled and excited.
Step-by-step explanation:
When the author uses words and phrases like "I can't contain my excitement about the upcoming trip!" "Fills my heart with boundless joy." or the general repeated use of the exclamation mark, along with some the author blatantly stating "I'm excited" in the beginning, you can tell the tone is excited. (Or thrilled. They both mean similar things in this context.)